Synthesis, structure, and electroluminescence of BR(2)q (R = Et, Ph, 2-naphthyl and q=8-hydroxyquinolato)

Three 8-hydroxyquinolato (q) boron compounds B(C2H5)(2)q (1), BPh(2)q (2), and B(2-naph)(2)q (3) have been synthesized by the reaction of 8-hydroxyquinoline with an appropriate BR3 compound. Compounds 1-3 have a tetrahedral geometry as demonstrated by the structure of 1 determined by a single-crystal X-ray diffraction analysis. Compounds 1-3 emit a green-blue color at lambda(max) = 495-500 nm when irradiated by UV light. The electroluminescent (EL) properties of 2 and 3 were examined by fabricating EL devices using 2 and 3 as the light-emitting layer, respectively. The devices of 2 produce a yellow-green light with broad emission spectra, attributed to the formation of an exciplex of 2 with the N,N'-di-1-naphthyl-N,N'-diphenylbenzidine (NPB) in the hole transport layer while the intrinsic EL emission of compound 3 was observed. Both 2 and 3 were found to be good electron transport materials in EL devices.